Thermal relay



Dec. 2,1924. 1,517,258

B. H. SMITH THERMAL RELAY Filed June 9, 1920 WITNESSES: INVENTOR QT Benjamin /7. 507/115 2 BY ATTORNEY Patented Dec. 2, 1924. i

UNITED. STATES PATENT OFFICE.

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To all whom it may concern:

Be it known that I,' BENJAMIN a citizen of the United States, and a resident of Wilkinsbur in the county of Allegheny and State of. ennsylvania, have invented a new and useful Improvement in Thermal Relays, of which the following is a: speclfi- 1 cation.,

-My invention relates to thermal relays and particularly to thermal relays that embody bimetallic members. I

One object of my invention is to rovide a thermal "relay that shall have sutiioient' time interval in the operation thereof to effect protection of electrical apparatus from overloads. I a

Onother object of my invention is to provide a relay", of the above-indicated character, that "shall embody means for increasing vide a relay. of the above-indicated charac' the heating, of the bimetallic member.

Another object of my invention is to proter, that shall be adapted for use in cartridge-type'fuse clips and be reliable and effective in its operation. I

Heretofore, considerable ditiiculty. has been encountered in developing sufiicient heat in a small bimetallic member that was traversed by the circuit current to obtain a movement that was s'uflicient to efiect satisfactory operation of a contact memberfor controlling an auxiliary'circuit. This dif- I ficulty was due to the fact that the current which traversed the bimetallic member was too small in value to develop the necessary amount of heat.

In view of the difli'culty of developing sufiicient heat in the bimetallic member for obtaining a movement of predetermined extent, I provide means for so multiplying the circuit current as to provide a current of I larger valuecfor heating the bimetallic member.

An auto-transformer or a transformer in which the windings are" entirely insulated from each other may be employed to'provide such magnified current for the bimetallic member. Since the heating developed in the bimetallic member is proportional to the square of the value of current that traverses the same, a greater degree of heat and, consequently, a greater bending force is obtained. y

Figure 1 of the accompanying drawings is a sectional view, partially in elevation, of a relay embodying my invention.

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Application mes June 9,1920. Serial m. senses.

- FigureQ is a diagrammatic view illustrating the connections between thetransformer windings and the bimetallic member.

for *permitting the interrupter 3. to interrupt the'circuit of the translating apparatus when the temperature of the latter attains or exceedsa predetermined value. The interrupter 3 is provided with an electromagnet 5 for maintaining theinterrupter in its closed position and a restraining spring 6 for opening theinterrupter 3 when the electromagnet 5 becomes de-energized. .The

circuit of the winding of the electromagnet 5 is controlledby the thermal device 4'.

The thermal device 4comprises a longitudinally slotted tubular member 7 of magnetizable material that has ferrules 8 and 9 disposed at the respective ends thereof and a plurality of windings 10 and 11 disposed around the tubular member and between the two ferrules.

and 13 of magnetizable material are dis- Two slotted circular disks 12 posed on the tubular member between the windings and the corresponding ferrules.

An enclosing shell. comprising a slotted tubular member 14 of magnetizable material and a tubular member 15 of insulating material'. is adapted to enclose the windings 10 and 11 and to complete the: magnetizable circuit that comprises the inner tubular member 7, the disk members12and 13 and the outer tubular member 14. a

.A bimetallic member 16 is supported by a bushing 17 that is disposed at one end of the tubular member 7 The movable end of the bimetallic member 16 base contact mem-, ber 18 mounted thereon that is adapted to contactively engage an adjustable contact member 19 of substantially cone shape that is disposed at the corresponding end of the tubular member 7. The adjustable contact member 19 is mounted in a bushing 20 that is disposed within, and supported by, the tubular member 7.

A terminal 21 of the windin 10 extends through the disk member 13 an is soldered to the ferrule 9. The other terminal 22 of the winding 10 is soldered to the tubular member 7. One terminal 23, of the winding 11, is also soldered to the tubular member 7 and the other terminal 24 is soldered to the ferrule 8. One terminal 25 of the bimetallic member 16 is connected to the terminal 21 that is soldered to the ferrule 9 and the other terminal 26 is connected to the tubular member 7. Thetubular member 7 is employed to provide a magnetizable core for the magnetic circuit and is also utilized to connect the terminal-22 of the winding 10 to the terminal 23 of the winding 11.

When the, relay 4 is connected in the circuit to be protected, the windings 10 and 11 which constitute the primary winding of the. transformer, are traversed by the current that traverses the circuit. The winding 10, which constitutes the secondary winding of the transformer, has its terminals connected to the respective terminals of the bimetallic member 16, and the current developed in the secondary winding 10 is thus caused to traverse that member.

The ratio' between the primary windings 10 and 11 and the secondary winding 10, of the transformer, is such that the value of the current which traverses the secondary winding and the bimetallic member is relatively greater than the value of the current which traverses the primary winding. The bimetallic member is thus heated by the current traversing it to a degree corresponding to the tem erature of the translating apparatus 1. hen the bimetallic member becomes heated to a predetermined degree which corresponds to the dangerous temperature in the translating apparatus 1, the contact member 18 is caused to disengage the adjustable contact member 19. The C11- cuit of the electromagnet 5 of the interrupter 3 is opened by the disengagement of the contact members 18 and 19, and the consequent de-energization of the electromagnet permits the interrupter 3 to be opened by the restraining spring 6.

The elements of the magnetic circuit comprisin 1 the slotted tubular members 7 and 14 an the slotted disk members 12 and 13 are so assembled that the slotted portions of the several elements shall coincide to preclude the development of eddy-current heat losses therein. The thermal efiect of the windings and of the hysteresis losses is distributed in the magnetizable material of the magnetic circuit and has substantially no effect on the operation of the bimetallic member.

The dead air space that surrounds the bimetalllc member 16 substantially preeludes the convection of heat from the tubular member 7 and the windings to the bimetallic, member. The relay 4 thus operates in accordance with the temperature conditions that are developed entirely by the current that traverses the bimetallic element and is not affected by any thermal losses in the windings and in the magnetic circuit of the transformer. The operation of the relay 4 is so actually dependent upon the transformer action that the removal of the outer tubular member 14 serves to make the relay ino erative.

lthough I have shown a preferred form of relay embodying my invention, I do not limit it to the s ific structure illustrated, as various modifications may be made therein within the spirit and scope ofmy invention, as set forth in the appended claims.

I claim as my invention:

1. A thermal relay for an electric circuit containing electrical apparatus constituting a unitary device adapted for insertion in fuse clips, and com rising a transformer and a bimetallic mem er, the primary winding of the transformer being in the electric circuit and the secondary winding being con- Bected in circuit with the bimetallic mem- 2. A thermal relay for an electric circuit containing electrical apparatus constituting a unitary device adopted for insertion in fuse clips, and comprising a transformer the primary winding of which is in circuit with the apparatus, and a thermal-respon sive member that is heated only by the current from the secondary winding .of the transformer.

3. A unitary thermal relay for an electric circuit comprising a magnetizable core member, a. primary and a secondary winding disposed therearound, a magnetizable shell disposed around the windings, athermal-responsive device enclosed within the magnetizable shell and heated by the current from the secondary winding, and means controlled by the thermal-responsive device for controlling an auxiliary circuit.

4. A thermal relay comprising means traversed by the current of an electric circuit, current-transformin means, means heated by the transforme current traversing the said transforming means, and means controlled by the heated means for controlling an auxiliary circuit.

5. A unitary thermal relay adapted for insertion in fuse clip terminals, comprising a translating device, a thermal-responsive device energized through the translating device and means controlled by the thermal device.

6. .A thermal relay comprising a magnetizable tubular member, a ferrule disposed at the respecti e ends the eof, a plurality of windings disposed around the tubular member between the ferrules, one of the windings being connected between the ferrules, a bimetallic member disposed within the tubular member and connected between the terminals of the other winding, and an adjustable contact member disposed adjacent one end of' the bimetallic member and adapted to be engaged thereby.

7. A thermal rela comprising a magnetizable shell, trans ormer windings magnetically associated therewith, athermal element disposed in and supported by the shell and means for heating the thermal element from one of the windings.

8, A thermal relay comprising a thermall -responsive element, a casing for maintainmg va dead air space therearound and for supporting the thermal-responsive element, an element traversed by the'current through the relay and means magnetically associated therewith to heat the thermal element.

9. A thermal relay comprising a thermally-responsive element, a casing of conducting material for maintaining a dead air space about the element, a second casing externally disposed with relation to the first casing and arranged to constitute a closed magnetic circuit with the first casing,.winglings magnetically associated with both casings to constitute therewith a transformer, and means for heating the thermally-responsive element from one of the windings.

10. A thermal relay comprising an enclosing casing having ferru es disposed at the ends thereof, a plurality of windings and a magnetically related shell of magnetizable material, and a thermally-responsive element heated by one of the windings.

11. A thermal rela for an electric circuit normally traversed y a current of relatively small value comprising a casing of magnetizable material, windings disposed in inductive relation theretov to constitute a transformer, one of saidv windings being traversed by the relatively small current, and a thermal element sup orted by the easing and connected to anot er of said windings to be traversed by a larger current.

' 12. In a thermal relay, the combination with a lurality of inductively related windings, 0 means com rising a magnetizable member for establis' ing a closed magnetic circuit about said windings, and a thermal element to be heated by one of said windings.

13. In a thermal relay, 9. pluralit of inductively related windings and a she I therefor comprising two concentrically disposed tubular members of magnetizable material and a; washer at each end disposed between the two tubular members.

14. In a thermal relay for an electric circuit, the combination with a thermally-responsive element, of a transformer comprising a primary and a secondary winding, respective y associated with the circuit and the thermal element, and means comprising a magnetizable. member serving as a closed magnetic ath between the windings, the magnetiza le member serving also to support the windings and to maintain a dead air space about the thermal element.

15. In a thermal relay, the combination .with a thermal element, of a transformer to control the heating thereof comprising a plurality of windings and a magnetic circuit therefor including two concentrically disposed slotted tubular members separated by slotted washers, the slots of the tubular members and the washers being disposed in one plane to preclude eddy currents therein.

16. A thermal relay for an electric circuit normally traversed by a relatively small current, comprising a thermally-responsive element'and means for amplifying the relatively small circuit current to effects. greater degree of heating in the thermal element.

. 17. A unitary thermal rotective device for'an electric circuit, a apted forinsertion in fuse-cli terminals, coin rising a casing, ferrules disposed at the en s thereof, a thermal element within'the casing, and means responsive to the circuit current for amplifying the heating effect thereof to effect a degree of heating in the thermal element greater than the heating that woul be effected by the circuit current.

18. In a thermal relay for an'electric circuit,-the combination with a thermally-responsive element, of a current-proportioningldevicecomprising means for maintaining a magnetic circuit substantially enclosing the thermal element, and means in fluenced by the circuit current for controlling the heating of the thermal element.

19. The method of obtaining a degree of heating in a thermal element incorrespondence withthe heating of an electrical apparatus normally traversed by arelatively small current, which consists in maintaining a substantially dead air space about the thermal element and then amplifying the relatively small circuit current to rovide a larger heating current for the t ermal element.

In testimony whereof,.'I have hereunto igggcribed my name this 4th day of June,

BENJAMIN H. SMITH. 

